Decoupling the Fermi-level pinning effect and intrinsic limitations on p-type effective work function metal electrodes

A review of literature combined with recent experimental results addressing the intrinsic and extrinsic factors controlling the effective work function (EWF) of metal gate electrodes on Hf-based high-K dielectrics is discussed. Through a systematic study including accurate extraction of EWF, our observations suggest, unlike popularly perceived, intrinsic E-f-pinning does not limit the EWF tuning on high-K. Also, a critical issue challenging the maintenance of high EWF metals at low effective oxide thicknesses (EOT), due to a new phenomena described as the V-fb roll-off, is reported for the first time. (C) 2007 Elsevier B.V. All rights reserved.